Eruptions of the Yellowstone volcanic system have included the two largest volcanic eruptions in North America in the past few million years; the third largest was at Long Valley in California and produced the Bishop ash bed.
On the diesel Passat, the TDI badge stands for Turbocharged Direct Injection, which isn't really all that helpful as the gasoline-powered Passat is also turbocharged and also uses direct injection. Volkswagen attempts to clear this up by calling this Passat the Passat TDI Clean Diesel.
Dieselgate: What VW TDI Owners Should Know. If youâre the owner of a so-called âclean dieselâ Volkswagen, the news that the automaker cheated its way into meeting emissions standards here and in Europe probably hit you with the force of a 2Ã4 to the back of the head. And if not, it should have.